The moon is moving further and further away from Earth, what's happening?

Accurate astronomical observations show that the Moon is gradually moving away from Earth at a rate of about 3.8 cm per year.

The Moon is gradually moving 'away' from Earth. A slow but relentless journey over the past 4.5 billion years - Photo: PIXABAY

At first glance, this number seems small, but when calculated over millions to billions of years, it represents a significant change that helps us better understand the history of Earth and the Moon's formation, as well as predict the future of the entire system.

How far is the Earth from the Moon, and how is it measured?

Determining the distance between the Earth and the Moon is not based solely on conventional observation. Scientists use laser distance measurement techniques (Lunar Laser Ranging).

During the Apollo missions and some Soviet spacecraft, reflective mirrors were placed on the surface of the Moon. When a laser beam was fired from Earth at the Moon, it would reflect back. By measuring the travel time of the light, scientists could calculate the distance precisely to the millimeter.

The results show that the current average distance is 385,000 km.

However, the Moon doesn't orbit the Earth in a perfect circle, but rather in an elliptical path, causing its distance to vary by more than 20,000 km. This is why sometimes a full moon appears larger than usual, a phenomenon known as a supermoon.

Tides: the driving force pushing the Moon away.

The primary reason the Moon drifts away is tidal force. The Moon's gravitational pull causes the water mass on Earth to expand, forming two "water holes," one facing the Moon and the other in the opposite direction.

However, because the Earth rotates faster than the Moon orbits it, these two water pockets are not aligned but are pulled slightly forward. This misalignment creates an additional gravitational force, pulling the Moon further away in its orbit and helping it move faster.

In return, the Earth has to make a sacrifice by slowing down its rotation. This means that the day on Earth is getting a little longer. The rate of change is tiny, only a few thousandths of a second per century, but when accumulated over millions of years, the difference becomes noticeable.

Going back in time, when the Moon first formed about 4.5 billion years ago, it was very close to Earth as a result of a massive collision between the early Earth and a celestial body roughly the size of Mars.

At that time, the moon appeared much larger in the sky than it does today, and its tidal influence was many times stronger.

Evidence from ancient geology and biology also confirms this. Fossilized shellfish show that 70 million years ago, a day on Earth lasted only about 23.5 hours, shorter than it is today. This is entirely consistent with predictions about the Moon gradually moving away and slowing down the Earth's rotation.

Future prospects

If this process continues, there will come a day when the Earth and the Moon enter a state called "double tidal locking": the Earth rotates on its axis so slowly that it coincides with the Moon's orbit around the Earth. At that point, only half of the Earth will always have a view of the Moon, while the other half will never see it.

However, this scenario will not materialize. In about a billion years, the energy emitted from the Sun will increase, causing the Earth to heat up and the oceans to evaporate. When the oceans disappear, tidal forces, the main driving force behind the Moon's drift, will also disappear.

Furthermore, billions of years from now, the Sun will swell into a red giant star, likely engulfing and destroying both Earth and the Moon.

The fact that the Moon is moving away from Earth at a rate of only a few centimeters per year may seem insignificant to everyday life. But from an astronomical perspective, this is a crucial process that helps scientists better understand the evolution of our planet.

It not only explains common phenomena like tides, supermoons, and solar eclipses, but also reveals a comprehensive picture of Earth's billions of years of history and predicts the fate of the Earth and Moon system in the distant future.

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MINH HAI

Source: https://tuoitre.vn/mat-trang-ngay-cang-roi-xa-trai-dat-dieu-gi-dang-xay-ra-20250916175347233.htm